The invention relates to a device and a method for detecting deposits on walls which are covered by a medium.
The formation of deposits on the walls of installation parts is a serious economic and technical problem in many cases. For example, germs which impair the product quality may form in deposits. Deposits may also influence the flow characteristic in fittings. In the case of pipelines, deposits cause a rise in the pressure loss and may even result in blockages in the case of small internal diameters. The material from which the walls are produced may also be damaged, depending on the type of deposit.
The walls on which deposits form may be produced from different materials, for example stainless steel or plastic. The surface structure of the walls influences the formation of deposits. Rough surfaces provide a better surface for deposits than smooth surfaces. The walls on which deposits form may be flat or curved. Inner walls of fittings, pumps, pipelines or containers, in particular, are technically relevant.
The media with which the walls are covered and from which the deposits are deposited may be liquid or gaseous. It is also conceivable for paste-like substances to cover the walls. The invention is preferably used with liquids, the use of the invention being particularly suitable for aqueous solutions.
The deposits may be either inorganic or organic substances. Important examples of inorganic deposits are carbonates, oxides or hydroxides which are deposited on the walls of installation parts as scale, rust or a mineral deposit.
The most important organic deposits are biofilms. The formation of biofilms is a significant problem in the field of hygiene technology, for example the production of food, pharmaceuticals or biotechnology. Growth is caused by biomass and by impurities in the biomass. Bacteria, fungi, yeasts, diatoms and monads are only a few organisms which cause the build-up of biomass. If the biofouling caused by these organisms is not controlled, it can disrupt process operations and have an adverse effect on the product quality. When producing foods and pharmaceutical products, strict purity levels must be complied with. Contamination with bacteria or metabolites of microorganisms may damage health.
Many processes in hygiene technology are operated discontinuously as batch processes. The production process is interrupted at certain intervals of time, which are often based on empirical values, in order to clean deposits from the installation. The duration of the cleaning process is likewise often based on empirical values. In order to economically optimize the production processes, the production phases should be as long as possible and the cleaning phases should be as short as possible. However, no impairment in the product quality must be accepted in this case.